Preheat oven to 350°. Line a 9×13 inch pan with foil and grease with cooking spray. In a large bowl mix together butter, brown sugar, and powdered sugar. Add flour and salt and mix until combined. Press firmly into prepared pan. Bake for 10 minutes.
Prepare the filling
While the crust is baking, combine eggs, Karo Syrup, sugar, melted butter and vanilla in a large bowl. Mix well. Stir in pecans. Pour over the crust, spread evenly, and return to oven to bake for 25-30 minutes longer until firm around the edges and center starts to firm up as well. Allow to cool completely before lifting the foil liner out of the pan and cutting into bars.
Drizzle caramel sauce over bars and sprinkle with sea salt to taste. Serve immediately or store in airtight container up to three days.